Wednesday, March 31, 2010

The south polar region of the Moon, with dark craters and high ridges, is a world away from the relatively smooth terrain visited by Apollo astronauts four decades ago. This rugged moonscape is the target for Europe’s next leap into space.

Two views from a high resolution (LROC Narrow Angle Camera) image of the floor of Apollo Basin, the large (see "The Biggest Deepest Crater," March 6) double-ringed impact crater in the southern hemisphere of the Moon's far side. This image shows part of the boundary between two flow units within the volcanic mare deposits on the crater's floor.

The sharp boundary between the topographically higher lavas on the right side of the image and the lower ones on the left reveals layers, suggesting that multiple volcanic events were involved in forming some of the isolated volcanic plateaus seen within the otherwise uniform crater floor lava flows. Both the high and low materials here are heavily covered in impact craters, indicating that these lavas, like much of the Moon's surface, are ancient. Many boulders can also be seen shedding out of the upper layers and eroding down onto the lower deposits. Image is 880 meters wide, and north is up. Part of NAC frame M114953774LE [NASA/GSFC/Arizona State University].

Unlike features on the nearside, craters and other landforms on the Moon's fars ide were only discovered beginning with the advent of the Space Age. Thus, many features have names that reflect more modern historical figures, places, and themes. One such example is the Apollo impact basin, a 538 km wide double-ringed impact crater in the southern hemisphere of the lunar far side, centered near 36°S, 208°E.

From a LROC Wide-Angle Camera mosaic (really worth a look here) showing most of Apollo Basin's northern, southern, and western inner ring as well as the central floor's dark mare basalt deposits. The white arrow shows the location of the high-resolution NAC image discussed above. The white "X", near the boundary of the smooth, dark floor deposits and the rougher, brighter inner ring highlands materials, is the center of one of the 50 Constellation Program ROI's or "regions of interest." The large (~51 km) crater at upper left is Dryden; the largest (~49 km) crater partially visible just to the left of center at the bottom of the mosaic is Chaffee. North is up, and the width of mosaic is 130 km [NASA/GSFC/Arizona State University].

This large feature was named in honor of the Apollo program (1968-1972), NASA's manned missions that culminated in twelve astronauts landing on the surface of the Moon, conducting scientific experiments and returning more than 380 kilograms of samples to Earth. Many individual craters within the Apollo Basin are named after deceased NASA astronauts and pioneers, including, more recently, craters named after the crews of the Space Shuttles Challenger and Columbia.

Apollo crater is an outstanding example of a concentric, double-ring impact structure, "transitional" in size, between smaller simple bowl-shaped and complex central peak or peak-ring craters and larger impact basins like Mare Orientale.

It is actually superimposed within the enormous, much older South Pole-Aitken (SPA) Basin, an impact structure that is one of the largest in the Solar System dominating the far side southern hemisphere. Apollo was selected as one of 50 sites for LRO to investigate in great detail as examples of the range of scientific questions and engineering challenges to be addressed in future human and robotic exploration of the Moon. The specific study area (centered on the white "X" in the WAC context image above) was chosen because of the presence of relatively rare far side deposits in close association with bright, presumably anorthositic highlands materials of the basin's inner ring of mountains.

Because the crater formed on the rim of the South Pole-Aitken Basin it's possible some of the materials excavated and uplifted by the Apollo Event may have originated at great depths, perhaps even down to the lunar mantle. The site also offers interesting operational challenges for astronauts and robotic missions, offering rare far side opportunities for science and exploration within both highlands and mare terrain.

Tuesday, March 30, 2010

A small secondary crater chain near the southwestern margin of Mare Orientale, within the Inner Rook Mountains. The ~125-meter-long chain is within one of fifty Constellation Program regions of interest (ROI) in the multi-ring Orientale basin. LROC's full Featured Image is ~530 meters across and the above image is a 212 meters wide swath of LROC NAC M112224591R [NASA/GSFC/Arizona State University].

This small chain of several craters likely formed from material ejected during the formation of a larger distant crater. The craters range from ~20 to ~30 meters in diameter and the entire chain is only ~125 m long. The irregular nature of the craters' floors and rims suggests that these are secondary craters rather than primary craters. Most chains of craters on the Moon are formed in this manner, but a few, like the 50-km-long Davy Catena (crater chain), are thought to have formed as a result of a series of impacts by fragments from a comet or asteroid that was disrupted when passing close to Earth.

The small crater chain lies inside of the Inner Rook Montes toward the south-western edge of Mare Orientale. Orientale 1 is one of two sites near the Orientale Basin identified as regions of interest to the Constellation Program. It is of interest because of the proximity of highlands regolith and the Orientale Basin impact melt sheet, which is heavily fractured to the north of the site, as well as for its location on the limb of the Moon as seen from Earth, making radio communications easier. Obtaining a sample of the impact melt would allow scientists to date the formation of the Orientale basin, one of the youngest large basins on the Moon.

The small white rectangle illustrates the location and range of the LROC Narrow-Angle Camera (NAC) image that includes the small crater chain in the LROC News System Featured Image, and the scale of this small portion of the Orientale basin (the oblong vent (middle left) is the center of the Orientale pyroclastic formation, a feature that dominates this area of interest. The south-southwestern Inner Rook Montes run across top of this part of the larger frame (the Outer Rook Montes are visible in the full LROC wide-angle camera (WAC) image. These two intact mountainous rings surround Mare Orientale. (LROC WAC image M102788066ME; north is up.) [NASA/GSFC/Arizona State University].

NAC image M112224591R was acquired on 7 November 2009 from an altitude of 53.5 km and has a pixel scale of ~0.55 m.

Saturday, March 27, 2010

Take away the rays, so distinctive to the Moon's geocentric and always apparent "near side" and what remains is a crater not unlike others elsewhere on our proportionally large natural satellite. The Queen of the Southern Highlands is young, only ~109 million years or so, as theorized by astronaut-geologist Harrison Schmitt and others (~100 ma) and then confirmed in far-flung samples of this mass-wasting event gathered by Cernan &Schmitt 2260 km away, during their "field expedition" also known as "Apollo 17."

Tycho's hemisphere-encompassing ray system isn't even unique on the Moon. Closer in to the impact, as seen in simple numbers instead of it sometimes blinding relative brightness some features in Tycho's immediate surroundings end up standing out in the image created. To the northeast are craters apparently flooded by molten material from down below.

Sasserides A, for example, is definitely not on anyone's hit parade of interesting nearside objects.

And even more ancient than Sasserides A or Tycho is the intervening and "tortured," partially filled-in crater with a southeastern rim joined at the hip to Tycho's northeast by an equally ancient, far smaller filled-in crater.

Each of these impacts (of the Pictet cluster) just don't stand out to our eyes, so close to Tycho. Sasserides and the others each had their day in the Sun, though, perhaps even outshining brazen Tycho in their time.

"Tycho's average depth below the rim is 4,700 meters. It has a central peak that rises 2,400 meters above the crater floor. Tycho and the craters surrounding it are part of the lunar southern highlands."

Tycho's ray system far outshines the impact itself. Not all its mysteries are fully understood. Do parallel twin rays suggest two progenitors, as suggested at Copernicus? As seen below definitive dating for the Tycho Event was hoped for and found by Cernan and Schmitt. The bright Tortilla Flats landslide material could, it was shown, be traced back to a "mass-wasting" pressure wave along a Great Circle route to Tycho, coinciding with surface material characteristics near Apollo 11, Surveyor 5 and Apollo 16. This most sampled of Tycho's rays is not, however, it's brightest [VMA v.5/Google Earth].

Notable sights along the trail of EVA 2 during the Apollo 17 expedition in Taurus Littrow Valley, including the brighter Tortilla Flats material later confirmed most likely to have originated in a landslide caused by the "mass-wasting" plasma shock wave that tore across the region during the Tycho Event. As now seems inevitable with space exploration, an equal number of important questions were raised by other evidence found while looking for this confirmation. Orange debris excavated from deeper under the surface by the Shorty impact, for example. Put together with other leads, the sharp eye of a single geologist on the ground saw and sampled something previously unrecognizable and invisible from orbit, and sharpened understanding of the Moon, and thus the Solar System and Earth in the bargain.

View Image & Learn more about Tycho Crater (and see it in visible images from the Lunar Reconnaissance Orbiter Camera).

Materials excavated during formation of this ~450 meter diameter impact crater have an unusual two-toned character, likely a reflection of heterogeneity in the target materials. Situated in Balmer Basin (18.341°S, 69.950°E), the crater is in an area thought to harbor a type of cryptomare an ancient volcanic surface later covered with lighter hued impact ejecta. The darker material may be basaltic rock excavated from deeper parts of the impact. The scene is a 540 meter subset of LROC NAC M111138159LE [NASA/GSFC/Arizona State University].

The Balmer Basin Exploration Region of Interest (ROI) lies within the Balmer Crater, centered at about 20°S latitude and 70°E longitude. Balmer is an old, highly degraded crater some 110 kilometers across and is part of a larger basin structure called the Balmer-Kapteyn Basin, which has 225 km and 450 km diameter outer rings. Scientifically, this area is interesting because it contains a type of 'light plains deposit' that appears to lie on top of an ancient basaltic surface. Building on earlier studies of these deposits, Hawke et al. [2005] concluded the deposits formed by the deposition of material ejected by later-formed impact basins mixed with regolith that had developed on the old Balmer volcanic lava flows. This conclusion was based on the occurrence of numerous 'dark haloed' impact craters, such as one seen in the LROC featured image of August 31, 2009.

LROC WAC mosaic of central Balmer crater, M104054832CE and it's location, as seen in a "departure angle" view of the lunar globe available in Google Earth [NASA/GSFC/Arizona State University].

Perhaps dark-haloed craters are not the only types that reflect this dichotomy. Two-toned deposits are evident in the crater shown in today's featured image. This distinctive two-toned appearance is seen in some other similar-size craters in Balmer, but is not common. The regolith here is probably fairly thick, perhaps 50 to 100 m in many places. The regolith is a zone of mixing between the light-toned basin ejecta deposits and the underlying basalts. This crater appears to have excavated both types of materials.

Buried volcanic deposits such as the ones in the Balmer region have been called 'cryptomare' after Head and Wilson [1992], who defined geologic features such as this as "covered or hidden mare deposits that are obscured from view by the emplacement of subsequent deposits of higher albedo." [see also the November 16, 2009 featured image release]

Compositional information gleaned from orbital remote sensing supports the interpretation that the light plains are underlain by mare basalt, particularly by the presence of higher iron oxide (FeO) and magnesium oxide (MgO) content than is typical of the surrounding highlands deposits.

Narrow-angle Camera (NAC) images show the detail of the crater ejecta from bright relatively young craters over a range of sizes that serve as natural drill holes into the light plains deposits. Explorers, whether human or robotic, visiting the Balmer region would determine the composition of the regolith excavated by these craters to test for a mixture of highlands and mare rock components. The age and composition of the basaltic components would reveal new insights into the volcanic history of the Moon.

Friday, March 26, 2010

The Soviet Union's Luna 16 descent stage, site of the first successful robotic lunar sampling mission and origination point for the return spacecraft, swept up by the Lunar Reconnaissance Orbiter (LROC) narrow-angle camera from an altitude of 124.18 kilometers, late in last summer's commissioning phase for the orbiter, September 2, 2009 (14,227 days after the soft landing) [NASA/GSFC/Arizona State University].

Luna 16 was the first robotic mission to land on the Moon and return a sample to the Earth. It was launched by the Soviet Union on 12 September 1970; landed on the Moon on 20 September; lifted off on 21 September and returned to the Earth on 24 September. The lunar landing occurred on the basaltic plains of Mare Fecunditatis; about 101 grams (3.5 ounces) of lunar material were returned. Sampling operations were conducted entirely in the dark since the Sun had already set when Luna 16 touched down (See below).

Tonight (late March 25, 2010 UT) the Luna 16 landing site bakes in mid-day equatorial sunshine near the eastern limb of a Moon waxing Full as seen from Earth, high overhead after sunset. Amazingly, as the inset showing the Moon's waning phase on Sept. 20, 1970, the robotic sampler was soft-landed, trapped its small but now-proven very valuable sample, and began its return trip to Earth in cold darkness, long after the local nightfall (with Earth, eternally hanging high over the western horizon, waxing Full) [Virtual Moon Atlas, v.5].

The high-altitude, relatively high-angled slew of LRO's fore-shortened view of this narrow-angle camera "target of opportunity," last September 2, left some detail at high contrast in the original commission-phase LROC frame "nacl00008ce6." Of course, the reduced quality of the calibrated version seen above in Google Moon is not a reflection of the image quality at present, in the product now labeled "M106511834." It's yet another tribute to the skill of the LROC team at Arizona State that the quality of the image today, originally imaged at a relatively high angle and from three times the LRO's present nominal mission altitude, made resolving the Luna 16 descent stage even remotely possible [Google/USGS/NASA/JAXA/GSFC/ASU].

A less-then-completely "notional" scene showing a 3D view of Luna 16 (with ascent stage still intact) as seen within the actual context of the present-day artifact's true surroundings on the Moon, made possible by the LROC and Google Earth.

Zoom into and explore Mare Fecunditatis and the sampling site of the landmark Luna 16 mission within LROC NAC image M106511834L, HERE. (LROC NAC Images of Luna 20, 23, and 24 can be found here).

Tuesday, March 23, 2010

Bang! On April 14, 1970 the Apollo 13 Saturn IVB (Saturn V Third Stage) impacted the Moon north of Mare Cognitum (-2.55°S, 332.12°E). The impact crater, roughly 30 meters in diameter, is clearly visible in LROC NAC image M109420042LE. Study of the rare impacts that can be definitively dated helps in determining rates of space weathering on every scale. The Apollo 13 SIVB impact shows a relatively wide ranging ray system, part of which may have resulted from hot plasma pressure waves. [NASA/GSFC/Arizona State University].

The Apollo 14 S-IVB (S-IVB-509) was 17.8 m tall, 6.6 m in diameter and weighing ~14,000 kg. Launched carrying Apollo 14 on January 31, 1971, after extraction of Lunar Module its remaining fuel was dumped and it was directed to impact the Moon on February 4. [NASA].

In April, the Apollo 13 Saturn V blasted off towards the Moon. The Saturn rocket consisted of a 3-stage launching system. While the first and second stage of the launch vehicle dropped back to Earth after launch, the third stage (S-IVB) was used to propel the docked Apollo Command Module and Lunar Module from Earth orbit into a lunar trajectory. The spent rocket booster then separated from the Command Module and later impacted the Moon. From the tracking of the radio signals of the rocket, the impact locations on the Moon and the impact times were fairly well known.

Seismogram of the Apollo 13 S-IVB impact recorded at the Apollo 12 seismic station in digital units (DU). The three traces designate the signal of the 3 orthogonal components of the ground motion at long wavelengths. The arrows mark the arrival times of the p (primary) and the slower s (secondary) seismic waves (image modified from: Ewing, M., et al., (1971), Seismology of the Moon and implications on internal structure, origin and evolution, in: De Jaeger (Eds.): Highlights of Astronomy, IAU, pp.155-172).

The impacts by the S-IVB stages represented unique calibration signals for the Apollo seismic station network, which operated on the lunar surface from 1969 - 1977. Since the rocket impacts occurred at known times and places, the seismic wave velocities, in particular those within the upper lunar crust could be measured directly.

At the time of the Apollo 13 mission, only the seismometer at Apollo 12 was available, which had been deployed 5 months earlier. The S-IVB impact occurred at a distance of 135 km from that seismic station.

AS12-46-5817 Until defunded in 1977, the Apollo 12 seismometer monitored levels of ground motion to detect arriving seismic waves. The instrument is protected by metal foil against the varying temperatures on the lunar surface that produce large thermal stresses. The Solar Wind Spectrometer is to the right of the Apollo Lunar Surface Experiment (ALSEP) Central Station, the Passive Seismic Experiment is to the left and the Lunar Surface Magnetometer is in the background, beyond and just to the left of the Central Station (NASA/Conrad/Apollo 12).

Analysis by the LROC team now have identified the craters associated with most of the rocket impacts in their predicted areas. Taking advantage of the precise LRO orbit and LROC pointing knowledge, it is now possible to determine the impact coordinates of rockets and their distances from the seismic stations more accurately to within a few hundred meters, over time as the orbit calculations are improved these estimates will in turn become more accurate. The precise impact coordinates may warrant a reanalysis of the seismic calibration data for improved models of seismic wave propagation within the Moon and the Lunar interior structure. The seismograph network recorded more than 13,000 seismic events and delivered some of the most important scientific results of the Apollo missions.

The Surveyor spacecraft (1966-1968) were designed to characterize lunar surface properties to help engineers design the systems astronauts would use exploring the Moon. Seven Surveyors were launched to the Moon and five succeeded in landing and returning useful data. Surveyor 1 landed in May 1966 and Surveyor 7, the final mission in the series, landed in January 1968.

Surveyor 6 Landed November 10, 1967 in Sinus Medii (0.5°N latitude, 358.6°E longitude), almost dead center on the near side of the Moon. One of its key experiments was measuring the surface chemistry with an alpha scattering detector, which showed the landing area to be basalt, similar to the surface measured by Surveyor 5. Surveyor 6 completed the data acquisition that the Apollo program needed and thus allowed Surveyor 7 to be sent to a site that was of higher scientific interest.

(Surveyor 4 was only 150 seconds from landing at the future landing site of Surveyor 6 the previous July when all contact was lost with the spacecraft during the terminal descent firing of its retro-rockets. Although it is believed Surveyor 4 exploded at that moment its official impact point, and a possible candidate for a LROC search for wreckage, is within 4 kilometers of Surveyor 6.)

The Surveyor 6 spacecraft survived one two week lunar night, but no significant data were returned after contact was reestablished on December 14, 1967.

Near the end of the nominal two week mission NASA engineers commanded the Surveyor 6 engine to fire for a few seconds. The spacecraft rose about 4 m above the surface and landed about 2.5 m from its original landing spot. This was the first successful liftoff from the lunar surface. And perhaps the only spacecraft to land twice on the Moon.

Diagram of the 6.5 second flight, or hop (diagram from the Boeing Company)

A quick note on lighting conditions.

Due to the Moon's slow rotation, the solar incidence angle is always changing at a a given site as LRO passes over. With time LROC can image a feature under varying lighting (from dawn to noon to dusk) thus providing a powerful tool for confidently identifying small features, such as the Surveyors, and fully understanding the subtleties of the local geology.

Surveyor 1 imaged by LROC under two very different lighting conditions. The background image (M122495769LE) was acquired with the Sun 67° above the horizon - the Surveyor is indicated with arrow and enlarged in the top inset. The lower inset shows the same Surveyor imaged with the Sun 14° from the horizon (M102443995LE) [NASA/GSFC/Arizona State University].

Images taken towards noon emphasize subtle differences in albedo (apparent reflectance or brightness) while images taken with the Sun low to the horizon bring out topography. From the high Sun images we see at all landing sites (Apollo, Surveyor, Luna) that the blast from the descent engines locally changed the surface albedo to varying degrees. This effect is mostly likely due to the engine plume rearranging dust particles of different sizes. The magnitude of the effect may be different in the highlands vs the mare.

Sunday, March 21, 2010

Surveyor 5 (At least we found the right image), swept up by the LROC narrow-angle camera on-board LRO during orbit 870, September 4, 2009, from 122.38 km over the southeastern Sea of Tranquility. (Three cheers to the LROC team for not leaving us hanging out on a limb for very long, also for superior patience and eyesight). The JPL-operated robotic lander built by Hughes Aircraft sits silently within the rim of a 10 meter crater (1.41°N 23.18°E) ~24 km northwest of Tranquility Base. (LROC NAC M106726943LE, resolution 1.24 m/p, width ~480 meters [NASA/GSFC/Arizona State University].

Surveyor 5 landed on Mare Tranquillitatis on September 11, 1967, in what must have been a harrowing touchdown. As pictures arrived on the ground it became apparent that the spacecraft had landed on the steep slopes of a small impact crater. After careful analysis of the images, including star field pictures, the Surveyor team was able to determine that the local slope was 19.7°!

The spacecraft performed all its assigned tasks, returning thousands of detailed pictures and measuring the chemistry of the soil. Less than two years after Surveyor 5 landed Neil Armstrong and Buzz Aldrin set down Apollo 11 Lunar Module Eagle less than 30 kilometers away, and gathered samples with chemistry similar to those measured by the Surveyor.

Find Surveyor 5 for yourself in the full resolution NAC image M106726943LE.

From among the commissioning and first of the nominal LRO mission LROC NAC imagery including published landing sites of five of the seven successful U.S. Surveyor robotic landers perhaps the most uncluttered include coordinates for Surveyor 7 (41°01′S, 348°35′E). Though the sun was late-morning high, the high-latitude southern highlands north of Tycho therefore presents distinct shadows for objects of sufficient profile. Though strewn with boulders of a similar-size only one object cast a diffuse shadow detached from it's source. For this and other reasons we speculate the object above is likely to be Surveyor 7, or more accurately the square solar panels seen as the elongated bright area set apart to the north of the larger and brighter object that is probably the main cluster of experiments. As astonishingly clear as the image is gray hues are balanced out and so the vehicle's three legs and other framework blend in with the surrounding lunar surface. These are also just below the 52 cm per pixel resolution. The view was from almost directly overhead though slewed two degrees) from 49.4 km altitude. Surveyor 7, last of the 1966-1968 series, managed by JPL, was soft-landed in January 1968 (M111668133LE from orbit 1590, October 31, 2009) [NASA/GSFC/Arizona State University].

Large Scale - The prominent Marius Dome field is a familiar target in amateur telescopes, changing almost from minute to minute 5 days after First Quarter or 4 days after Last Quarter, as the terminator sweeps across the western Oceanus Procellarum. Their prominence is quickly lost outside of the long shadows of a low sun of their remarkably low profile. The area was on tap as a landing site for Apollo prior to the cancellation of Apollo 18, 19 & 20. With the help of the latest fleet of vehicles and experiments, including the Laser Altimeter and sophisticated cameras aboard LRO, complex interrelationships between Marius and other artifacts of volcanism on the Moon are again being deciphered. LROC NAC Image M102508144LE [NASA/GSFC/Arizona State University].

Small Scale: Marius Hills is the largest volcanic dome field on the Moon. The region is an area of high interest because it contains approximately half of the Moon's known volcanic domes. These domes range from 200-500 m in height. In comparison, the Hawaiian volcano Mauna Loa, which is the largest shield volcano on Earth, is 17,170 m tall. This LOLA image covers the area of the Moon from 9.5 - 17N°, and 303.5 - 311°E [NASA/GSFC].

The Luna 21 spacecraft landed in Le Monnier crater on 15 January 1973 delivering the Soviet Union’s second rover - Lunokhod 2 to the lunar surface (LROC Image of Lunokhod 2 rover). Luna 21 had a landed mass of 1900 kg and is about 2.3 m long; its overall diameter is about 3.3 m including the landing legs. The NAC image shows the typical descent engine scour around the vehicle with a bright zone extending out some 10-20 m.

The landing site is 5-6 km north of the mare highlands boundary; the rolling hills of the highlands are visible in the distance from the lander.

Russian Academy of Sciences

The lander is oriented northwest and the rover drove off in that direction. Its tracks are clearly visible. Several maneuvers were made around the lander to examine the local terrain and photograph the lander.

Friday, March 19, 2010

Is this Surveyor 5? We won't stake any reputations on it, but it fits the profile as recorded in post-mission reports. The high-sun image of the official location, barely more than 20,000 meters north-northwest of Apollo 11, makes a dicey identification. At 1.4 degrees north of the equator, little if any shadow is cast and the resolution of this commission-phase LROC image is around 1.2 meters per pixel, leaving little detail. Later images, with twice the resolution, all fell just beyond this official location. This Surveyor might be an interesting future landmark for missions to study the landing site Apollo 11 without disturbing that area, though even a landing here would have some impact on the "pristine" conditions at Tranquility Base [NASA/GSFC/Arizona State University].

Editor's note. Knowing full well the full cycle of the Surveyor saga, we earlier erroneously labeled this posting as a speculation concerning a possible sighting of Surveyor 7, and the last in the series, which of course landed north of the rim of Tycho. It wasSurveyor 5that landed 23.9 kilometers northwest of what would eventually become the landing sight of Apollo 11, 22 months and 9 days later (September 11, 1967). We're just glad no one had to point out the error to us.

Descent stage of Lunar Module 11, Orion of Apollo 16, as imaged in the harshest kind of lunar mid-day sun from only 46.81 kilometers overhead (LRO-target-Sun phase angle "f" of 7.77°). Using the NASAView program (v3.6, Jan. 2010), available from the Planetary Data System (PDS), a direct sample of the raw LROC NAC image (M113853974LE - ~51.7 cm per pixel) even a very brief exposure time of only three ten-thousandths of a second was sufficient to capture defining glare of processed metallic and man-made materials against a blindingly bright albedo of surrounding lunar surface, the Cayley Plains material situated between North and South Ray crater (8.9730111°S 15.5001889°E), north of the Descartes swirl and lunar magnetic anomaly. Though it may be the best direct views so far of Apollo 16 our first glance might mislead. Was all the rich detail of the terrain sacrificed to capture (slightly from the North) the historic artifacts of Young & Duke's expedition of April 1972? Unlike a tourist at the Grand Canyon, the LROC team can't immediately change the exposure and take the same shot again [NASA/GSFC/Arizona State University].

Not quite. After running the 400 line by 800 sample (~196 x 408 meter) area through the clumsy auto-correct feature of the open-source Paint.NET program we see arguably one of the best views yet of astronaut footprints on the lunar surface. The dark circle brought out, around Orion's descent stage is from descent exhaust but mostly from foot-fall, almost obscuring the larger vehicle and virtually invisible in the raw image higher above. As it is, the trails taken by Young and Duke, exposing less-space-weathered material below the immediate surface, trace out and around Orion's landing struts and the other objects nearby like the U.S. flag, camera, and ALSEP [NASA/GSFC/ASU].

Thursday, March 18, 2010

That's because we thought, until recently, that the Moon was just about the driest place in the solar system. Then reports of moonwater started "pouring" in – starting with estimates of scant amounts on the lunar surface, then gallons in a single crater, and now 600 million metric tons distributed among 40 craters near the lunar north pole.

"We thought we understood the Moon, but we don't," says Paul Spudis of the Lunar and Planetary Institute. "It's clear now that water exists up there in a variety of concentrations and geologic settings. And who'd have thought that today we'd be pondering the Moon's hydrosphere?"

Spudis is principal investigator of NASA's Mini-SAR team – the group with the latest and greatest moonwater "strike." Their instrument, a radar probe on India's Chandrayaan-1, found 40 craters each containing water ice at least 2 meters deep.

Right: A Mini-SAR radar map of the lunar north pole. Craters circled in green are believed to contain significant deposits of frozen water. [more]

"If you converted those craters' water into rocket fuel, you'd have enough fuel to launch the equivalent of one space shuttle per day for more than 2000 years. But our observations are just a part of an even more tantalizing story about what's going on up on the Moon."

It's the story of a lunar water cycle, and it's based on the seemingly disparate – but perhaps connectable – results from Mini-SAR and NASA's recent LCROSS mission and Moon Mineralogy Mapper (M3 or "M-cubed") instrument also on Chandrayaan-1.

"So far we've found three types of moonwater," says Spudis. "We have Mini-SAR's thick lenses of nearly pure crater ice, LCROSS's fluffy mix of ice crystals and dirt, and M-cube's thin layer that comes and goes all across the surface of the Moon."

An amazing spacecraft gently settled to the lunar surface on 17 November 1970. It carried the first successful robotic lunar rover -- Lunokhod 1. For the next ten months the rover was driven by operators in the Soviet Union, with the total distance traveled exceeding 10 km. For comparison, in six years of operation the Mars Exploration Rover Opportunity has traveled about 12 km.

The Lunokhod rovers are approximately 2.3 meters long and 1.5 meters tall.

After landing, the rover drove down a ramp onto the lunar surface and tested its eight wheels. The rover was driven by solar power during the day; at night it parked and relied on thermal energy from a polonium-210 radioisotope heater to survive the cold (-150°C).

The intrepid rover sent back valuable data concerning the composition of the regolith (soil), close up views of the local topography, and important engineering measurements of the regolith. Examine the full NAC image and trace out the path of Lunokhod 1.

Two years later (January 1973) Luna 21 landed in Le Monnier crater, delivering an upgraded Lunokhod 2. It sported higher resolution cameras and an improved scientific payload. Like its predecessor, it was driven by engineers on Earth during the day, and parked at night. Lunokhod 2 explored the Moon for about four months. Unfortunately, the mission was brought to an early end due to overheating, perhaps when soil got on the rover and covered key components.

Lunokhod 2 rover, note its tracks tracing its route southward. The enlargement is specially stretched to show the form of the rover, the brightest area may be the open clam shell lid; NAC Image M109039075LE [NASA/GSFC/Arizona State University].

The two Lunokhods showed the value of robotic explorers on the surface of another world. It would be another 24 years before the next robotic rover, Sojourner, drove on another world - this time Mars. The next lunar rover, 40 years later, is scheduled for 2013, a joint venture between India and Russia.

Old friends receive a visitor

Recently the LROC Science Operations Center received an unexpected visitor - Ruslan Kuzmin. He was one of the scientists who had actually participated in the Lunokhod missions! We were able to show him LROC pictures of the hardware on the surface and he was gracious enough to write down some of thoughts upon seeing his "old friends".

"Thank you very much for showing me the excellent LROC images of the Lander platform from “Luna-21”, as well as the robotic lunar rover “Lunokhod-2” in its last and eternal parking place after a 37-km, 4 month journey of research.

"To see the images with Lunokhod-2 and its tracks on the lunar surface is a very special feeling for me. In the time of the Lunokhod-2 operation, I was a young planetologist who was participating in the mission, and I analyzed the images received by the rover’s TV- cameras. In actual fact, this was the first successful mission in which I was involved. It was 37 years ago (in the last century!) when the Lunokhod-2 traveled for four months within the crater Le Monnier at the eastern edge of the Mare Serenitatis."

"While looking at LROC images of the Lunokhod-2 rover, I felt a deep interior excitement due to the welled up memories of the earliest “pages” of my science career. It is very exciting that the Lunokhod-2, as well as many other American and Soviet Union Landers, which operated many tens of years ago, now might be imaged by LROC so clearly, and viewed by millions of people around the world. The LRO camera is without any doubt a really fantastic instrument that simultaneously brings our eyes close to the lunar surface, while reminding us of pioneering results from historical missions.

"P.S. In attachment I sent the fragment of the Lunokhod-2 panoramic image of the Fossa Recta - the last object of its research."